NAME

SYNOPSIS

DESCRIPTION

[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C
standard.

The fclose() function shall cause the stream pointed to by stream to be flushed and the associated file to be
closed. Any unwritten buffered data for the stream shall be written to the file; any unread buffered data shall be discarded.
Whether or not the call succeeds, the stream shall be disassociated from the file and any buffer set by the setbuf() or setvbuf() function shall be
disassociated from the stream. If the associated buffer was automatically allocated, it shall be deallocated.

[CX] If
the file is not already at EOF, and the file is one capable of seeking, the file offset of the underlying open file description
shall be set to the file position of the stream if the stream is the active handle to the underlying file description.

The fclose() function shall mark for update the last data modification and last file status change timestamps of the
underlying file, if the stream was writable, and if buffered data remains that has not yet been written to the file. The
fclose() function shall perform the equivalent of a close() on the file
descriptor that is associated with the stream pointed to by stream.

After the call to fclose(), any use of stream results in undefined behavior.

RETURN VALUE

Upon successful completion, fclose() shall return 0; otherwise, it shall return EOF [CX] and set
errno to indicate the error.

ERRORS

The fclose() function shall fail if:

[EAGAIN]

[CX]
The O_NONBLOCK flag is set for the file descriptor underlying stream and the thread would be delayed in the write operation.

[CX]
The process is a member of a background process group attempting to write to its controlling terminal, TOSTOP is set, the calling
thread is not blocking SIGTTOU, the process is not ignoring SIGTTOU, and the process group of the process is orphaned. This error
may also be returned under implementation-defined conditions.